The present invention relates to a clamping apparatus for positioning and fixing work pieces to be machined on a work table of a machine tool. The invention may be particularly useful for a wire erosion machining apparatus. In particular, the invention concerns a clamping apparatus comprising at least one clamping rail member adapted to be attached to the work table of the machine tool, and at least one work piece holder adapted to be clamped to the clamping rail member in a well defined position.
If a tool or a work piece to be machined has to be clamped to a work table of a machine tool, usually, in a first step, the tool and the work piece, respectively, are fixed to a pallet and, in a second step, the pallet is clamped to a chuck member. The chuck member itself is, in most cases, rigidly attached to the machine tool. The actuation of the clamping elements of the chuck member is usually performed manually, electro-mechanically, pneumatically or hydraulically.
The document EP-B-0 202 452 discloses a fixing and reference system for a wire spark erosion machine. This fixing and reference system comprises reference elements in the form of flat, plate-like strips made of hardened steel, adapted to be attached to the work table of the wire spark erosion machine. The cross section of these reference elements is essentially dovetailed, whereby the top surface has a larger width than the bottom surface. The reference element comprises a side surface adjoining the top surface, extending in a right angle both to the top and bottom surfaces and constituting the Y-direction reference. Moreover, the reference element comprises several continuous bores adapted to receive bolts, by means of which the reference element can be fixed to threaded bores provided in the work table of the machine tool. The X-direction reference is constituted by a block-like portion fixed to the front surface of the reference element and having a stop surface. A work piece to be clamped on the work table is positioned against the side surface adjoining the top surface of the reference element and clamped by means of clamping members. Such a fixing and reference system probably is useful for lighter work pieces. Moreover, the fabrication of the reference elements is laborious and expensive.
The document U.S. Pat. No. 5,019,129 discloses a holding system for a work piece having a clamping frame provided with a fixed and a movable clamping jaw. A fixture provided on the machine tool comprises a dovetailed protrusion to which is attached a fixture plate having a corresponding recess. The fixture plate is adjustable and can be held in position by a clamping mechanism. An adapter is attached to the fixture plate, provided with a dovetail as well and to which a clamping frame can be attached. The clamping mechanism for holding the fixture plate in position comprises spring-biased pins as well as a locking screw.
The document EP-A-1 402 985 discloses a clamping apparatus comprising a frame member and attached to the work table of a machine tool. The frame member is provided with two lateral legs and with a distance member inserted therein between. Moreover, the frame member comprises two guide elements running between the two lateral legs. A lockable slide member is movably guided by the two guide elements. The slide member is adapted to receive and clamp work pieces.